Battery element containing efficiency improving additives

ABSTRACT

A battery element of a lead acid battery including a negative plate, a positive plate and a separator having a metal inhibiting additive associated with a plate that reduces the detrimental effects of at least one impurity on the negative plate.

RELATED APPLICATION

[0001] This application is a division application of application SerialNumber 09/045,725, filed Mar. 20, 1998. This earlier filed applicationis incorporated in its entirety herein by reference.

BACKGROUND OF THE INVENTION

[0002] The present invention relates to an improved lead acid batteryelement containing metal impurity inhibiting polymeric additives, whichare added to the positive active material, negative active materialand/or battery separator to inhibit the detrimental effects of certainmetals on the efficiency of a lead acid battery, particularly thenegative plate battery element and to macroporous additives that enhanceactive material utilization efficiency and improvement in theutilization of sulfuric acid electrolyte necessary for the dischargereaction of a lead acid battery.

[0003] Metal impurities can be introduced into a lead acid batterythrough the use of any of the materials used in the manufacture of thebattery. For example, metal impurities can be introduced in the lead andleady oxides used in the manufacture of the active material, thematerials of construction including the lead grids, alloying agents,electrolyte and water. Nearly all metallic impurities, if they arenobler than lead, have a smaller hydrogen overvoltage than pure lead.Therefore, they increase hydrogen evolution even if they are depositedin minute concentrations on the surface of the negative plates. Thesemetals cause a continued gas evolution even after charging is completed.Hydrogen is evolved on the deposited metal with low hydrogenovervoltage, which can be short-circuited with lead. The effect of metalon the gassing particularly postcharge gassing decreases in thefollowing sequence: Pt, Au, Te, Ni, Co, Fe, Cu, Sb, Ag, Bi and Sn. Thepresence of 0.3 ppm of platinum in the acid can cause a doubling of theself-discharge rate. Tin can produce this effect at 0.1%. Freshlydeposited antimony is especially active. Besides the discharge of thenegative plates with concomitant hydrogen evolution, these materialsalso move the end of charge voltage of the negative plates toward morepositive values. The hydrogen evolution increases with rising aciddensity. Because the hydrogen overvoltage decreases with temperature,the self-discharge increases.

[0004] In addition, antimony is often added to grid lead in order tomake the lead more fluid and more easily cast into the shapes necessaryfor storage battery grids. Further, it also hardens the resultingcasting so that it can be further processed in the plant without damage.In certain battery applications, it may be necessary for the battery towithstand extreme resistance to corrosion of positive plate grids. Inthat event, higher antimony contents typically within the range of 4.5to 6 percent are incorporated into the grid to form a lead antimonyalloy. Antimony in these concentrations are generally only used inpositive grids particularly grids intended for corrosion resistantbatteries. Corrosion resistance typically means the ability to withstandthe destructive effects of excessive charge or overcharge.

[0005] Antimony in the grid metal produces a definite effect on thecharge voltage characteristics of the fully charged wet battery. Thehigher the antimony percentage in the grid metal, the lower the chargevoltage and conversely, as the antimony is decreased so the chargevoltage increases until pure lead is attained, which produces thehighest voltage on charge. Since the use of antimony has gradually beenlowered from a maximum of about 12.0% to a maximum of about 6.0%antimony, the charge voltage of average batteries has increased.

[0006] Contaminant metals, hereinafter referred to as metal impuritiesincluding antimony from the positive grids, during service life, slowlygoes into solution in the sulfuric acid electrolyte and from there it isbelieved to electroplate onto the surface of the negative plates. Oncethere, it acts as an additional electrode with the grid and the leadactive material of the negative plates. This combination creates localaction, promoting self-discharge and contributes to poor wet batteryshelf life. In addition, the battery's charge voltage slowly decreasesduring life and, in the voltage regulated electrical circuit of a car,the difference between the two becomes greater. The car voltageregulator is set at a voltage just slightly higher than the normalcharge voltage of the battery. Thus, the generator is able to restoreelectrical energy to the battery, as needed, to keep it charged. Withmetal deposition and the lowering of the battery charge voltage, thegenerator output into the battery increases as an overcharge, whichhastens the deterioration of the battery in service, until failureoccurs. Therefore, it is very desirable to inhibit the detrimentaleffects of antimony on the negative plate.

SUMMARY OF THE INVENTION

[0007] A new battery element which inhibits the detrimental effect ofsoluble metal impurity on the negative plate has been discovered. Inbrief, the battery elements include the addition of an organic polymerhaving functional groups with a preferential affinity for the metalimpurity in the cation or anion state, to the positive active material,the negative active material or the separator which separates thepositive and negative plates within a lead acid battery and whichtypically is a reservoir for sulfuric acid electrolyte.

[0008] A new battery element, which improves utilization efficiency ofthe active material in a lead acid battery has been discovered. Inbrief, the battery elements include the addition of macroporouscontaining particle additives to the active material in the positive ornegative plates of a lead acid battery to improve overall utilizationefficiency and the utilization of sulfuric acid electrolyte duringdischarge of the battery.

DETAILED DESCRIPTION OF THE INVENTION

[0009] In one broad aspect, the present battery elements comprise theaddition of an organic polymer containing functional groups with apreferential affinity for metal impurity in the cation or anion state tothe positive active material, the negative active material and/or theseparator which separates the positive plates from the negative platesin a lead acid battery. In a preferred embodiment, the organic polymersare porous, i.e. the porosity of the polymer allows the soluble metalimpurity in the electrolyte to contact both the outer surface of thepolymers and the internal surfaces created by the porosity of theorganic polymers. The functional groups having a preferential affinityfor metal impurity include both functional groups on the outer surfaceand internal surfaces in contact with soluble metal impurity in theelectrolyte. The metal impurity inhibiting additives are typicallyincorporated into the negative active material, the positive activematerial and/or the separator in an amount sufficient to inhibit thedetrimental effects of metal impurity on the negative plate.

[0010] In another broad aspect, the present battery elements comprisethe addition of macroporous additives to the active material present inthe positive and/or negative plates in a lead acid battery. In a furtherpreferred embodiment, the macroporous particles have a reduced affinityfor bonding with the active material in the positive and negativeplates, i.e. a substantially reduced bonding of lead ion with thepolymeric functional groups.

[0011] As set forth above, metal impurities can be introduced into thebattery during the battery manufacturing process, particularly in thestarting materials used for battery manufacture. Many of the metalimpurities can exist in the anion or cation form i.e. a negative orpositive charge respectively in sulfate solutions such as thatrepresented by sulfuric acid electrolyte. Depending on the molarity ofthe sulfuric acid electrolyte and the metal impurity, such cation/anionforms can change as the molarity changes. Depending on such sulfuricacid molarity, it is believed that platinum, gold, thallium, nickel,cobalt, iron, copper, antimony, silver, bismuth and tin can exist asanions even though such existence as anions may be weak or unstable.Further, such anion forms may predominant at the sulfuric acidelectrolyte concentrations, which exist after battery charging. One ofthe particularly detrimental metal impurities is platinum.

[0012] As set forth above, such metal impurities can be introduced intothe lead acid battery during manufacturing. In a number of batterydesigns, grid materials not having antimony as an alloying agent areused for battery manufacture. However, even in these types of batteriesusing nonantimony containing grids, antimony can be introduced as animpurity in the starting materials for battery manufacture including thestarting lead and leady oxide type materials.

[0013] As set forth above, antimony, which is present in the positivegrid as an alloying agent, can be oxidized and/or corroded to form asoluble antimony ion, which diffuses and/or migrates to the negativeplate. Antimony at the negative plate can produce a number ofdetrimental problems such as self discharge and gassing particularlyhydrogen formation. Antimony ion from the positive grid can exist inboth the anion and cation form, i.e. a negative or positive chargerespectively. It is believed that the form of the anion or cation isdependent on the oxidation state of the antimony, i.e. +3 or +5, themolarity of the sulfuric acid and the battery voltage. For example, itis believed that antimony can exist as SbO2+ cation and Sbo3−anion inthe antimony +5 state and as SbOS04−, Sb(SO4) ²⁻SbO2 in the antimony +3state. These +3 anion forms are believed to exist when the molarity ofthe sulfuric acid is greater than one but may not exist at the fullyrecharged battery voltage. In addition, it is believed that antimony mayexist as Sb+3 or SbO+ in the antimony +3 state again depending onmolarity and battery voltage. As set forth above, the sulfuric acidelectrolyte participates in the discharge reactions taking place in thelead acid battery. Thus, the wt% sulfuric acid can decrease from 30-40wt% sulfuric acid to from 10-14 wt% sulfuric acid depending on the typeof battery design and the initial sulfuric acid concentration in theelectrolyte. The amount of sulfuric acid remaining will be dependent onthe percent of discharge of the battery with less sulfuric acidremaining when batteries are discharged to 80% or more.

[0014] The organic polymers having functional groups with a preferentialaffinity for metal impurities in the anion or cation state inhibit thedetrimental effects of soluble metal impurity on the negative plate.While the exact mechanism of inhibition is not known, it is believedthat the metal impurity anion or cation is bound by the functional groupsuch as by the anion replacing the anion present on the functional groupin an anionic polymer or by a cation replacing the cation when theorganic polymer contains cation functional groups. Although anion and/orcation replacement is believed to be one mechanism for inhibiting theadverse effects of metal impurity ions, metal impurities can also formcomplexes and/or be solvated to inhibit the detrimental effect of metalimpurities on the negative plate and such mechanisms are included inthen the term inhibiting. One of the major discoveries of the batteryelements of this invention is the inhibition of metal impurities overthe varying sulfuric acid molarities and battery potentials (voltages)that occur during the charge discharge reactions in a lead acid battery.Further it has been discovered that the metal impurity which has beeninhibited by the organic polymer additive is not substantially anddetrimentally desorbed and/or released from the polymer under thesulfuric acid molarity and battery voltage conditions and changes in alead acid battery, that is the metal impurity inhibition continuesduring a plurality of charge/discharge reactions within the battery.

[0015] As set forth above, the organic polymers containing functionalgroups can introduce cations and/or anions into the battery elementwhich cations or anions can be displaced by the metal impurity anionand/or cation. Further, the affinity of the organic polymer having suchmetal impurity inhibiting functional groups have a stronger bindingand/or complex formation and/or salvation of metal impurity ions whencompared to any intermediate soluble lead ions such as lead +2 which maybe formed during the conversion of solid lead, solid lead peroxide toinsoluble lead sulfate. As is known by those having skill within thelead acid battery art, cations and/or anions which are displaced bymetal impurity cations or anions should not introduce any substantialdetrimental effects on battery performance.

[0016] As set forth above, one of the classes of organic polymers hasfunctionality, which have affinity for metal impurity in the cationform. The metal impurity cation displaces the cation associated with thefunctional group. Typically, the cation displaced can be hydrogen ionor, for example, sodium ion. The organic polymers having such cationfunctionality can be further classified as strongly acidic cationpolymers or weakly acidic cation polymers. Particularly preferredstrongly acidic cation polymers are those containing sulfonic acidgroups or their sodium salt i.e. sulfonic groups preferably in thehydrogen form. Typical examples of polymers containing the sulfonic acidand/or sulfonate functionality are those derived from polystyrenecrosslinked divinylbenzene, phenol-formaldehyde polymers and other likearomatic containing polymers.

[0017] As set forth above the organic polymer can have differentfunctional groups such as functional groups containing strongly acidicfunctionality such as ,ulphonic and phosphonic functionality on the sameorganic polymer. As set forth above, strongly acidic cation polymers arepreferred for inhibiting the effects of metal impurities. A particularlypreferred functionality on the polymer is phosphonic acid and/orphosphonate here in after refered to as phosphonic functionality.Typical examples of such functionality are:

[0018] where R is typically hydrogen or sodium ion, preferably hydrogen.

[0019] In general the phosphonic functionality can be incorporated intothe polymer matrix by chemical reaction including grafting of suchfunctionality, on for example the aromatic portion of polystyrene and/orphenol-formaldehyde polymers. In addition, the functionality can beincorporated by the copolymerization unsaturated vinylmono or gem ofphosphonic acid or ester monomers with other monomers patricularlystyrene, with still other monomers such as acrylate or acrylovitriletogether with a cross-linking agent such as divinylbenzene. A typicalmonomer used for such copolymerization is vinylidene diphosphonic acidor the ester thereof to produce gem phosphonic functionality. Furtherexamples of such polymers are polymers having a plurality of aminoalkylene, phosphonic acid or phosphonate associated with the organicpolymer.

[0020] As set forth above bis-derivatives are also useful includingimino-bis(methylenephosphonic acid). The particularly preferredfunctionality is amino methylelephosphonic acid groups on polystyrenecross-linked with divinylbenzene.

[0021] As set forth above, phosphonic functionality can be incorporatedinto the polymer by reaction with an existing polymermatrix or bycopolymerization of for example a vinyl phosphonic monomer. A preferedpolymer is one containing polymerized styrene monomer either as a homepolymer or an inter polymer with other polymerized monomeric units. Suchpolymers containg polymerized styrene are generally referred to aspolystyrene polymers.

[0022] As set forth above the organic polymer can have differentfunctional groups such as functional groups containing strongly acidicfunctionality such as sulphonic and phosphonic functionality on the sameorganic polymer.

[0023] The weakly acidic cation polymers in general have carboxylicfunctionality and/or the sodium salt associated with the organicpolymer. Typical examples of such polymers are those derived fromunsaturated carboxylic acids such as acrylic, methacrylic or maleiccrosslinked with another monomer such as divinylbenzene or ethylenedimethacrylate. The preferred organic polymers containing cationfunctionality are the strongly acidic cation polymers having sulfonicacid functionality.

[0024] As set forth above, the organic polymer can have functionalityhaving a preferential affinity for soluble metal impurity anions, i.e.the anion associated with the functionality is displaced by the solublemetal impurity anion in the electrolyte. The organic polymers havinganion functionality can have both strongly basic and weakly basic anionfunctionality. Typical examples of strongly basic anion containingfunctionality are those having an ammonium functionality associated withthe organic polymer. As set forth above, the anion associated with thefunctionality, typically sulfate or chloride, is displaced by the metalanion within the electrolyte. Typical ammonium groups associated withthe polymer include trimethyl ammonium ion and dimethylethanol ammoniumion. Other groups include isothiouronium and derivatives thereof.Typical examples of organic polymers are polystyrene cross-linked withdivinylbenzene. The ammonium ion with an appropriate anion can beattached directly to, for example, the aromatic ring of the polystyreneor through, for example, a methylene bridge. Typical examples of weaklybasic polymers having anion functionality are polymers, which containtertiary aliphatic or aromatic aliphatic amine functionalities on thepolymer such as polystyrene or a polyunsaturated carboxylic acids. Suchpolymers are typically cross-linked with a cross-linking agent such asthe cross-linking agents referred to above. Further, the polymer basicanion functionality can be obtained through aliphatic polyaminecondensation reactions to produce the organic polymer. Typically, theweak base anion resins contain primary, secondary and/or tertiary aminegroups generally as a mixture. Typical examples of such amine groups aretrimethyl amine and dimethylethanolamine. The preferred organic polymershaving anion type functionality are the strongly basic anion containingfunctionality particularly for their strong binding and low release ordesorption of metal impurity properties preferably having ammoniumfunctionality, particularly for incorporation into the negative plates.Since the electrolyte in the lead acid battery is sulfuric acid, it ispreferred to use sulfate as the anion to be displaced by metal anion.

[0025] As set forth above the organic polymers can contain primarysecondary or tertiary amine groups including aliphtaic polyamenefunctionality. Further as set forth above, such organic polymers cancontain aliphatic amine functionality. Further, as set forth above suchpolymers can contain amine functionality with acid functionality.Particularly preferred functionalities associated with the organicpolymer which contain both amine and acidic functionality are thosecontaining secondary and tertiary amine functionality and strong acidfunctionality, such as for example, the examples set forth above.

[0026] A particularly preferred class of aliphatic aromatic aminefunctionality are those having amino pyridine groups associated with theorganic polymer. Examples of such groups can be represented by theformula.

[0027] where in R is preferably an aliphatic substituent, an aliphaticpolyamino substituent or a 2-picolene containing substituent R′ ispreferably alkylene, preferably methyleneand R″ is a non-substantiallyinterfering substituent, preferably hydrogen. Particularly preferredadditives are organic polymers having functionality from 2-picolylamine,N-methly-2-picolylamine, N-2hydroxyethyl)-2-picolylamine,N-(2-methylaminoethyl)-2-picolylamine and bis-(2-picolyl)amine.

[0028] The aromatic aliphatic amine functionalities particularly the2-picolylamine, such as bis-(2-picoly)amine, are particularly useful ininhibiting the detrimental effects of copper and nickel.

[0029] As set forth above the organic polymers can contain primarysecondary or tertiary amine groups including aliphtaic polyamenefunctionality. Further as set forth above, such organic polymers cancontain aliphatic amine functionality. Further, as set forth above suchpolymers can contain amine functionality with acid functionality.Particularly preferred functionalities associated with the organicpolymer which contain both amine and acidic functionality are thosecontaining secondary and tertiary amine functionality and strong acidfunctionality, such as for example, the examples set forth above.

[0030] The organic polymers having functional groups with affinity formetal impurity are typically within the particle size ranges,porosities, surface areas, additive concentration and such otherphysical properties set forth below with respect to porosity additives.The porosity of the preferred organic polymers can vary over a widerange such as within the ranges set forth below with respect to microand macro porosity. The porosity of the preferred organic polymers isthat which allows the metal impurity ion, cation and/or anion topermeate the organic polymer particle thereby affording good contactwith the functional groups attached to the external and internalsurfaces of the particles. The total displacement capacity of theorganic polymer having such functional groups is typically greater thanone milliequivalent of displaceable anion or cation per gram of polymer,preferably greater than three and still more preferably greater thanfive.

[0031] Any suitable positive active electrode material or combination ofsuch materials useful in lead-acid batteries may be employed in thepresent invention. The positive active electrode material can beprepared by conventional processes. For example, a positive activeelectrode material precursor paste of lead sulfate and litharge (PbO) inwater can be used, or conventional pastes, such as those produced fromleady oxide, sulfuric acid and water, can be used. After the paste isapplied to the grid material, it is dried and cured. The precursor pastemay be converted to lead dioxide by applying a charging potential to thepaste.

[0032] Any suitable negative active electrode material useful inlead-acid batteries may be employed in the present invention. Oneparticularly useful formed negative active electrode material compriseslead, e.g., sponge lead. Conventional lead paste prepared from leadyoxide, sulfuric acid, water and suitable expanders can be used.

[0033] Each of the cells of a lead acid battery further includes anon-electrically conductive separator acting to separate the positiveand negative electrodes of the cell and to hold electrolyte. Anysuitable material may be used as a separator provided that it has nosubstantial detrimental effect on the functioning of the cells orbattery. Typical examples of separator material for batteries includeglass fiber, sintered polyvinyl chloride and microporous polyethylene,which have very small pore sizes. Certain of these separators are formedas envelopes, with the pasted plates inside and the separator edgessealed permanently. Typically only the positive plates are encased inthe separator. Separators uses for sealed lead-acid batteries operatingon the oxygen recombination principle, i.e., oxygen recombinantbatteries include one or more layers of silica-based glass, preferablyseparators formed of a highly absorptive porous mat of acidwettablebinder free microfine glass fibers. Typically, a mix of fibers may beemployed whose individual fibers have an average diameter in the rangeof a bout 0.2 to about 10 microns, more preferably about 0.4 to 5.0microns, with possible minor amounts of larger gauge fibers tofacilitate production of the mat. The porosity is preferably high, morepreferably in the range of about 80% to about 98% and still morepreferably about 85% to about 95%, if in the compressed state in thecell (slightly higher in the uncompressed state). The separatorpreferably has a relatively high surface area, more preferably in therange about 0.1 to about 20 m2/g, which facilitates the absorption andretention of relatively large amounts of acid electrolyte volumetricallywhile, if desired, still having a substantial unfilled pore volumepermeable to oxygen for transport directly through the separator forconsumption at the negative electrode. The particularly preferredseparator materials have a surface area as measured by the BET method ofin the range about 0.2 to about 3.0 m2/g., 30 especially about 1.0 toabout 2.0 m2/g.

[0034] As set forth above metal impurities are particularly detrimentalin sealed lead acid batteries operating on the oxygen recombinationprincipal, i.e. recombinant batteries. A number of impurity metals canexert a deleterious effect on the performance of recombinant batteriesby for example, effecting one of more of the performance requirements ofthe recombinant batteries such as by increasing oxygen, evolution at thepositive electrode, increasing hydrogen evolution at the negativeelectrode, inhibiting oxygen recombination at the negative electrode andin increasing the amount of water lost by the battery. Typical examplesof metals that are particularly deleterious in recombinant batteries arearsenic, antimony, cobalt, chromium, nickel and tellurium.

[0035] As set forth above, the metal impurity inhibiting additives canbe incorporated directly into the positive active material or negativeactive material for reducing the detrimental effects of the solublemetal impurity on the negative plates. Further, the metal impurityinhibiting additives, as set forth above, can be coated on the separatorsuch as the glass fiber mats used in lead acid batteries. Further, themetal impurity inhibiting additives can be incorporated into the porouspolymeric separators, such as polyvinyl chloride and microporouspolyethylene. Typical concentrations of the additives associated withthe separator is less than about 10 wt% preferably less than about 5 wt%basis the weight of the separators. The preferred metal impurityinhibiting additives are the porous organic polymers, which allow forthe inhibiting effect of the additives while not detrimentally adverselyeffecting the flow of electrolyte from and/or through the separator tothe positive and negative plates.

[0036] In another broad aspect for manufacturing tin dioxide coatedporous substrates, the process comprises contacting a porous substratewith a composition comprising a tin oxide precursor, such as tinchloride forming components, including stannic chloride, stannouschloride, tin complexes and mixtures thereof, preferably stannouschloride, at conditions, preferably substantially non-deleteriousoxidizing conditions, more preferably in a substantially inertenvironment or atmosphere, effective to form a tin oxideprecursor-containing coating, such as a stannous chloride-containingcoating, on at least a portion of the substrate. The substrate ispreferably also contacted with at least one dopant-forming component,such as at least one fluorine component, at conditions, preferablysubstantially non-deleterious oxidizing conditions, more preferably in asubstantially inert atmosphere, effective to form a dopant-formingcomponent-containing coating, on at least a portion of the substrate.The coated porous particles are particularly useful in a number ofapplications, particularly lead acid batteries, for example, monopolarand bipolar batteries, catalyst, resistance heating elements,electrostatic dissipation elements, electromagnetic interferenceshielding elements, electrostatic bleed elements, protective coatings,field dependent fluids and the like. In practice the particles which arepreferred for use in such applications in general have an average lengthin the range of from about 20 microns to about 7 mm and an averagethickness in the range of from about 20 microns to about 7 mm, theaverage length and thickness being different or the same depending onparticle geometry and application. As set forth above, the substrate canbe optimized for a particular application and the particular electricaland/or mechanical requirements associated with such end use application.For example, in applications in which the particles are combined withother materials, such as polymers and positive active material of a leadacid battery and depending on the requirements of the application,ranges of from about 3 microns to about 300 microns, or even less thanabout 5 microns, typically ranges of from about 3 microns to about 150microns or from about 5 microns to about 75 microns are useful. Theporous inorganic substrates, can be characterized by bulk density(gm/cc) which is the weight or mass per unit volume considered only forthe particle itself, i.e., includes the internal pore volume, surfacearea (M2/gm), total pore volume (cc(hg)/gm), pore size distribution andpercent apparent porosity. In general, it is preferred that the bulkdensity be from about 3% to about 85% more preferably from about 10% toabout 70%, more preferably, from about 10% to about 60% of the truedensity of the substrate material. Bulk densities less-than about 5% arealso useful. In addition, the porous substrate can have a wide range ofsurface area (M2/gm) of from about 0.01 to about 700 preferably having amoderate to high surface area, preferably, from about 10 M2/gm to about600 M2/gm, more preferably, from about 50 M2/gm to about 500 M2/gm.

[0037] The pore volume is preferably from about 0.4 cc/gm to about 3.5cc/gm, or even up to about 5 cc/gm, more preferably from about 0.7 cc/gmto about 4.5 cc/gm more preferably from about 0.7 cc/gm to about 3.25cc/gm. The pore size distribution can vary over a wide range and canhave various distributions including multi-modal, for example,bi-modadistribution of pores including macro pores and micro pores.There ideally exists a relationship between pore diameter, surface areaand pore volume, thus fixing any two variables generally determines thethird. In general, the mean (50%) pore diameter for macro pores, i.e.,generally classified as having a pore diameter greater than about 750angstroms can vary from about 0.075 microns to about 150 microns, morepreferably, from about 0.075 microns to about 10 microns. Microporosity, generally classified as a porosity having a mean pore diameterof less than about 750 angstroms can vary over a wide range. In general,the mean pore diameter for micro porosity can vary from about 20angstroms to about 750 angstroms, more preferably, from about 70angstroms to about 600 angstroms. The ratio of macro to micro porositycan vary over a wide range and depending on the application, can bevaried to provide optimized performance as more fully set forth underthe various applications. In general, the ratio of percent macroporosity to micro porosity expressed as that percent of the totalporosity can vary from abaut 0% to about 95%, more preferably, fromabout 5% to about 80% macro porosity and from about 100% to about 5%,more preferably from about 95% to about 20% micro porosity.

[0038] As set forth above, the porous substrate can be inorganic forexample, carbon and carbide, i.e., silicon carbide, sulfonated carbonand/or an inorganic oxide. Typical examples of inorganic oxides whichare useful as substrates include for example, substrates containing oneor more alumino silicate, silica, alumina, zirconia, magnesia, boria,phosphate, titania, ceria, thoria and the like, as well as multi-oxidetype supports such as alumina phosphorous oxide, silica alumina, zeolitemodified inorganic oxides, e.g., silica alumina, perovskites, spinels,aluminates, silicates, e.g., zirconium silicate, mixtures thereof andthe like. A particularly unique porous substrate is diatomite, asedimentary rock composed of skeletal remains of single cell aquaticplants called diatoms typically comprising a major amount of silica.Diatoms are unicellular plants of microscopic size. There are manyvarieties that live in both fresh water and salt water. The diatomextracts amorphous silica from the water building for itself whatamounts to a strong shell with highly symmetrical perforations.Typically the cell walls exhibit lacework patterns of chambers andpartitions, plates and apertures of great variety and complexityoffering a wide selection of shapes. Since the total thickness of thecell wall is in the micron range, it results in an internal structurethat is highly porous on a microscopic scale. Further, the actual solidportion of the substrate occupies only from about 10-30% of the apparentvolume leaving a highly porous material for access to liquid. The meanpore size diameter can vary over a wide range and includes macroporosityof from about 0.075 microns to 10 microns with typical micron sizeranges being from about 0.5 microns to about 5 microns. As set forthabove, the diatomite is generally amorphous and can develop crystallinecharacter during calcination treatment of the diatomite. For purposes ofthis invention, diatomite as produced or after subject to treatment suchas calcination are included within the term diatomite.

[0039] As set forth above, porous substrate particles can be in manyforms and shapes, especially shapes which are not flat surfaces, i.e.,non line-of-site materials such as pellets, extrudates, beads, includingspheres, flakes, aggregates, rings, saddles, stars and the like. Thepercent apparent porosity, i.e., the volume of open pores expressed as apercentage of the external volume can vary over a wide range and ingeneral, can vary from about 20% to about 92%, more preferably, fromabout 40% to about 90%. In practice, the bead particles, includingspheres, which are preferred for use in certain applications in generalhave a roundness associated with such particles generally greater thanabout 70% still more preferably, greater than about 85% an still morepreferably, greater than about 95%. The bead products of this inventionoffer particular advantages in many of such applications disclosedherein, including enhanced dispersion and rheology.

[0040] Acid resistant inorganic substrates, especially fibers, flakes,and glass fibers, are particularly useful substrates, when the substrateis to be used as a component of a battery, such as a lead-acidelectrical energy storage battery.

[0041] The porous substrate for use in lead-acid batteries, because ofavailability, cost and performance considerations, generally comprisesacid resistant glass, and/or ceramics more preferably in the form ofparticles, for example, fibers, and/or flakes, and/or beads includingspheres and/or extrudates as noted above. The solid substrates includingorganic polymers for use in lead-acid batteries are acid resistant. Thatis, the substrate exhibits some resistance to corrosion, erosion,oxidation and/or other forms of deterioration and/or degradation at theconditions present, e.g., at or near the positive plate, negative plateor positive or negative side of bipolar plates or separator, in alead-acid battery. Thus, the substrate should itself have an inherentdegree of acid resistance. If the substrate is acid resistant, thephysical integrity and electrical effectiveness of the whole presentbattery element, is better maintained with time relative to a substratehaving reduced acid resistance. If glass or ceramic is used as thesubstrate particle, it is preferred that the glass has an increased acidresistance relative to E-glass. Preferably, the acid resistant glass orceramic substrate is at least as resistant as is C-or T-glass to theconditions present in a lead-acid battery. Preferably the glass containsmore than about 60% by weight of silica and less than about 35% byweight of alumina, and alkali and alkaline earth metal oxides.

[0042] As set forth above, one of the preferred applications for use ofthe porous substrates is in lead acid batteries. Thus, the substratescan be added directly to the positive active material of a lead acidbattery, i.e., the positive electrode to improve battery performance,particularly positive active material utilization efficiency. Oneparticular, unique aspect of the porous substrates is that the substrateis able to provide an internal reservoir for holding sulfuric acidelectrolyte required for carrying out the electrochemical reactions inthe positive active material. More particularly, the porosity improvesoverall, high rate performance of the positive active material, i.e.improved utilization efficiency at varying rates of discharge time,including high rates and at short discharge times.

[0043] As set forth above, the physical properties of the poroussubstrates can vary widely. It is preferred that the substrate havesufficient macro porosity and percent apparent porosity to allow for theutilization of the electrolyte sulfuric acid contained in the poresduring discharge of the positive active material and, in addition, thatthe bulk density be selected to reduce the overall weight of thepositive active material while enhancing the overall performance of thebattery. In general, the preferable percent apparent porosity can varyfrom about 40% to about 92%, more preferably, from about 70% to about90%. The preferred ratio of percent macro porosity to percent microporosity can vary over a wide range and in general is from about 20% toabout 95% macro porosity, more preferably, from about 45% to about 90%macro porosity with the balance being micro porosity. The mean porediameter, particularly mean macro pore diameter, can vary over a widerange with the utilization of electrolyte during the condition of thedischarge of the battery being an important factor i.e., at high ratedischarges, such as cold cranking, high macro porosity is preferred.Preferred mean macro pore diameter is from about 1 micron to about 150microns, more preferably, from about 5 to about 100 microns or even fromabout 0.075 micron to about 10 micron and still more preferably fromabout 0.1 to about 5 microns.

[0044] As set forth above, a particularly preferred substrate is aporous particle, i.e. porous support, particularly beads, includingspheres, extrudates, pellets, rings, saddles, stars, etc., preferablywithin the bulk density, macro porosity, micro porosity, apparentpercent porosity and surface areas as set forth above. The coatedparticles can provide improved performance in various applications,particularly, in the positive active material of lead acid batteries. Asset forth above, the porous substrate can provide a reservoir forelectrolyte sulfuric acid, which participates in the electrochemicalreaction during discharge of the positive active material. Aparticularly unique embodiment of the present invention is the use ofthe porous substrate itself as an additive in the positive activematerial to provide a reservoir of electrolyte sulfuric acid whileproviding a light weight additive for incorporation into the positiveactive material. Such particles are porous and within the ranges as setforth above particularly the preferred ranges. Such porous substratescan be further coated with additional components such as with othersurface components, which may improve recharge, i.e. oxidation as wellas other conductive components. As set forth above, the porous substratewith or without an additional component provides unexpected improvementin the performance of the positive active material, particularly, in thehigh rate discharge conditions such as cold cranking under lower thanambient temperature conditions.

[0045] Another particularly unique embodiment of the present inventionis the use of the porous substrate itself as an additive in the negativeactive material to provide a reservoir of electrolyte sulfuric acidwhile providing a lightweight additive for incorporation into thenegative active material. Such particles are porous and within theranges as set forth above for the porous substrates particularly thepreferred ranges. Such porous substrates can be further coated withadditional components such as other surface components, which mayimprove recharge, discharge and/or overall life of the battery, such asconductive components which are stable at the conditions of the negativeelectrode such as carbon and conductive metals, which coated poroussubstrates are included within the scope of this invention and the termporous substrate. The porous substrate with or without an additionalcomponent provides unexpected improvement in the performance of thenegative active material particularly under cold cranking conditionsparticularly multiple cold cranking under lower that ambient temperatureconditions. As set forth above, the porous substrate can provideunexpected improvement in cold cranking typically 0 degrees F or lowerduring a series of multiple cold cranking. In addition, the poroussubstrates in the negative active material can provide for improvedactive material surface area maintenance and active material morphologymaintenance particularly at elevated temperatures such as from about60-80 degrees C or higher.

[0046] Typically, the porous substrates with or without additionalcomponents are incorporated into the positive and negative activematerial typically at a concentration of up to about 5-wt%, typically upto about 3-wt% basis the active material.

[0047] As set forth above, it is preferred that the porous substrateparticles have sufficient macroporosity and percent apparent porosityfor the utilization of the electrolyte sulfuric acid contained in thepores during discharge of the active material. Further, as set forthabove, the preferred mean macropore diameter is from about 0.075 micronsto about 10 microns and still more preferably from about 0.1 to about 5microns. Particularly preferred solid porous particles that exhibitsufficient macroporosity to allow for improved utilization of sulfuricacid electrolyte are silica containing inorganic oxides preferablydiatomites particularly those as set forth above and organic basedmaterials particularly polyolefins still more preferably polypropylene.

[0048] As set forth above, the porous substrates are acid resistant andinclude a wide variety of materials, including inorganic and organicbased materials. The porous substrates can be in a wide variety ofshapes, including shapes that are reduced in size during the manufactureof the positive active material, such as in the blending and/or mixingof the porous substrate in positive active material manufacture. It ispreferred that the resulting particles if reduced in size maintainporosity parameters within the ranges as set forth above. It is alsopreferred, that the particles have sufficient stiffness and orresistance to detrimental permanent deformation in order to maintainsufficient porosity for the sulfuric acid in the pores to participate ina number of repetitive discharge and charge cycles, such as greater than50 cycles or even 100 cycles.

[0049] Further unique embodiment of the present invention is the use ofa resilient organic porous substrate which resists detrimental permanentdeformation maintains sufficient porosity for the sulfuric acid in thepores, has resiliency to be deformed under the conditions of dischargeparticularly mechanical forces in the active material of the lead acidbattery and has resiliency to approach or attain its original geometryupon recharge of the battery. In a lead acid battery, the densities ofthe active material change i.e. lead at a density of 11.34 gram/cc, leadperoxide at a density of 9.4 grams/cc, (negative and positive platerespectively) change during discharge of the battery to lead sulfatehaving a density of 6.2 grams/cc i.e. lead sulfate. Upon recharge, thelead sulfate is converted back to lead and lead peroxide in the negativeand positive plates respectively. The resilient organic poroussubstrates have the ability to be deformed during discharge and approachor attain their original geometry during recharge of the battery. Thechanges in density and the ability of the porous substrate to bedeformed allows for increased availability and a greater amount ofsulfuric acid from the pores of the substrate as a function of time toparticipate in a number of repetitive discharge and charge cyclesleading to increased utilization efficiency. Typical examples ofresilient organic porous substrates are elastomeric or rubber-likeporous substrates wherein the pores allow the sulfuric acid toparticipate in discharge and charge cycles. Further examples of suchorganic resilient porous substrates are organic polymers including forexample organic polymers selected from the group consisting ofpolyolefins, polyvinyl polymers, -phenol formaldehyde polymers,polyesters, polyvinylesters, cellulose and mixtures thereof. Thepolymers are selected to be acid resistant and compatible with theactive material at the conditions of the electrode in which they are incontact. Various resilient organic porous substrates particularly porousparticles can be produced using suspension polymerization of a dispersedphase consisting of monomers, cross-linking agents, initiators i.e.catalysts and a co-solvent that functions to aid pore formation. Theparticle size, pore volume, pore size distribution and macroporosity canbe varied within the ranges as set forth above. Such resilient organicporous substrates including particles as set forth above have geometriesand are typically used within the ranges as set forth above for thecoated porous substrates, particularly the preferred ranges and, as setforth above, as to their use in positive active and negative activematerial. Depending on the particular active material in which suchresilient porous substrates are incorporated, such porous substrates canbe further coated with additional components such as with other surfacecomponents, which may improve overall properties such as discharge,recharge and life of the active materials.

[0050] As set forth above, the porous substrates including resilientporous substrates can be incorporated into the positive and negativeactive material. The various porous substrates provide a reservoir ofelectrolyte sulfuric acid in the active material. The reservoir ofsulfuric acid in the porous substrates can be added to the poroussubstrate prior to the addition of the porous substrate to the positiveand negative active material or incorporated into the porous substratefrom the sulfuric acid electrolyte present in the lead acid battery.Further, other liquids such as water can be substituted for sulfuricacid if a liquid is added to the porous substrate prior to the additionof the porous substrate to the active material. As is recognized bythose of skill in the art, only liquids which do not have an adversedetrimental effect on the performance of the battery should be added tothe porous substrate prior to addition to the active material.

[0051] In a still further embodiment and as is set forth above, theporous substrate particles can be coated with another material. One suchmaterial is a component which gives hydrophobic character to the poroussubstrate, i.e. the porous substrate with the component is not water wetto the same degree as without the component. Such change to hydrophobiccharacter can enhance the flow of electrolyte within the active materialby limiting the bonding of the active material to the pores present inthe porous particles and to particle surfaces. A particularly preferredcomponent is a silica based size having hydrophobic alkyl groups such asmethyl, ethyl or isooctyl which provide for hydrophobic character on thesurface of the porous particles. Many of the organic porous particleswithin the scope of this invention have inherent hydrophobic propertiessuch as the polyolefins whereas others have a combination of hydrophilicand hydrophobic properties. As set forth above, it is preferred that theporous particles have sufficient hydrophobic character to reduce thepermanent bonding of the active material to the surfaces of the porousparticles particularly the pores of the particles. The reduced bondingof the active material to the porous particles allows for improveddiffusion of the sulfuric acid electrolyte to the interior of the activematerial associated with the positive and/or negative plate.

[0052] As set forth above, the additives are typically incorporated intothe positive and negative active material at a concentration of up toabout 5-wt%. The porous particle additives and the antimony inhibitingadditives are incorporated during battery manufacture preferably duringthe production of the paste prior to application on the grid material.The additives can be incorporated into, for example, the lead, leadyoxide powders to which the sulfuric acid and water are added.Alternatively, the additives can be mixed into the precursor paste priorto applying on the grid material. It is preferred that the additives beincorporated such as to provide a uniform distribution of the additiveparticles throughout the entire paste, active material.

[0053] Further, the porous substrate as set forth above can be an acidresistant organic material, including organic polymeric materials as setforth above. Preferred polymers are polyolefin polymers, polyvinylpolymers, phenolformaldehyde polymers, polyesters, polyvinylesters andmixtures thereof. Preferred polymers are polyolefins, preferablypolypropylene, phenolformaldehyde polymers and polyvinylester,particularly modacrylic polymers.

EXAMPLE 1

[0054] A separator battery element is manufactured from a glass-mathaving a nominal thickness of 48 mils and a microporous rubber separatorhaving a thickness of 85 mils. The glass-mat and rubber separator have amean pore diameter less than 5 microns. A powdered organic polymerhaving a size distribution of from 50 to 125 microns prepared frompolystyrene and cross-linked with divinylbenzene having amino methylenephosphonic functional groups, is sprayed onto the glass-mat in anaqueous slurry. A noninterfering polymer is incorporated into the slurryand has an electrostatic charge opposite that of the metal inhibitingpolymer. The charge differences allow the formation of a porous floc onthe glass-mat.

[0055] The glass-mat and separator are combined by the application of anadhesive followed by mat compression. The organic polymer having thephosphonic functional groups is on the interior of the glass-mat facingthe inner surface of the separator. The separator is assembled into a12-volt battery with 6% anitmony grids for positive plates and negativegrids containing no antimony. Trace amounts of nickel are also presentin the lead. The detrimental effects of nickel and antimony on thenegative plate are inhibited by the additive in the separator.

EXAMPLE 2

[0056] A separator battery element is manufactured from a glass-mathaving a nominal thickness of 48 mil. and a microporous polyethyleneseparator having a thickness of 85mils. The glass-mat and separator havea mean pore diameter less than 5 microns. A powdered organic polymerhaving a size distribution of from 50 to 125 microns prepared frompolystyrene and cross-linked with divinylbenzene having gem phosphonicfunctional groups, is sprayed onto the glass-mat in an aqueous slurry. Anoninterfering polymer is incorporated into the slurry and has anelectrostatic charge opposite that of the metal inhibiting polymer. Thecharge differences allow the formation of a porous floc on theglass-mat. The glass-mat and separator are combined by the applicationof an adhesive followed by mat compression. The organic polymer havingthe phosphonic functional groups is on the interior of the glass-matfacing the inner surface of the separator. The separator is assembledinto a 12-volt battery with 6% antimony grids for positive plates andnegative grids containing no antimony. Trace amounts of nickel is alsopresent in the lead. The detrimental effects of nickel and antimony onthe negative plate are inhibited by the additive in the separator.

EXAMPLE 3

[0057] The separator element of example 1 was modified by using a secondmicroporous glass-mat as a replacement for the rubber separator. Theseparator is assembled into a 12-volt battery using the same negativeand positive grid plates as example 1. The detrimental effects of nickeland antimony on the negative plate are inhibited.

EXAMPLE 4

[0058] A macroporous amino phosphonic divinylbenzene cross-linkedpolystyrene additive was compounded with a number of different polymermaterials used commercially for the manufacture of battery separators.This additive was designed at a particle size distribution to provideincreased surface area for the additive and to be electrolyte accessiblein the separator polymer matrix.

[0059] The porosity of the polymeric matrix was designed so that theadditive was present in the channels and pores of the separator and wasaccessible to the electrolyte as opposed to the additive being totallysurrounded and encapsulated by the polymeric matrix.In the latter casethe additive would not be accessible to the metal contaminate dissolvedin the electrolyte. A number of different polymeric separators wereevaluated including a polyethylene separator, a natural rubbercompounded separator and a polyvinyl chloride separator. The separatorswere evaluated in a continuous filtration column in order to determinethe binding efficiency and capacity of the additive as a function of thetype of additive, it's concentration and the accessibility of theadditive in the polymeric matrix to electrolyte.

[0060] In the evaluation protocol, two blank polyethylene separatorswere mounted first on a four-inch diameter filtration column in order tobe able to better control the solution flow through the column device.

[0061] Solution flow rate was also controlled via a vacuum applied tothe collection vessel. The solution flow rate that allowed separators tobe characterized for overall metal binding efficiency was 0.5 ml/min. Ontop of the polyethylene separators was placed four polyvinylchloride(PVC) separators containing 3.9-wt% additive and weighing a total of15.2 grams. In the apparatus, the PVC separators were caulked withsilicone material at the column interface in order to prevent leakage. Astock antimony (III)soln. was used in all evaluations and had aconcentration of 20.4 mg/L SB (III) ion in 30-wt.% sulfuric acid. A 1-cmliquid level was maintained on the separator by continuous addition ofsolution, to provide a constant pressure. The filtrate through thecolumn was monitored every 60 minutes to determine the concentration ofantimony in the filtrate. Over the first two and one-half hours, theantimony level in the filtrate was below the detection of the ICP unit.At four and one-half hours, there was a residual concentration of 0.7mg/L of antimony. This represents a 97% capture efficiency over the lasthour on a single pass. The data obtained using the additive at the sameconcentration as would be present in the separator showed a captureefficiency on 94% on a single pass. In this control evaluation, theadditive was distributed on the top of the polyethylene separatorfollowed by applying two standard PVC separators (without additive) inorder to hold the additive in place. The conclusions from the test wasthat the distribution of the additive in the PVC separator was moreuniform compared to what can be done in the laboratory with theunincorporated additive.

[0062] The major advances that are shown are that the additive is highlyefficient for irreversible binding of antimony when incorporated intothe PVC separator and that the separator manufacturing procedureprovides a very uniform distribution of the additive in the pores andchannels typically greater than 1 micron. Furthermore, the additive washighly accessible to the electrolyte. It was also found that a reducedparticle size and increased surface area improves overall additiveeffectiveness.

[0063] The test protocol was repeated for a polyethylene separatorhaving relatively small pores and a natural rubber compounded separator.The results on capture efficiency showed a very low capture efficiencyfor the polyethylene separator compounded with 7.5-wt% additive and arelatively low to moderate capture efficiency for the natural rubberseparator which has intrinsic metal control capacity from the rubber. Apost mortem analysis was done on both the PVC and polyethylene separatorand it was determined that the manufacturing process for thepolyethylene separator showed total encapsulation of the additive withvery fine pores less than 0.1 microns and that the additive was notsubstantially electrolyte accessible. The photomicrographs for the PVCseparator showed essentially the entire additive particle accessible tothe electrolyte within the pores and channels of the separator.

EXAMPLE 5

[0064] An evaluation protocol was undertaken to determine theirreversible binding of a metal impurity silver at a typical acidconcentration of 38-wt% sulfuric acid. The sulfuric acid solution had21.4 parts per million (ppm)of silver ion and 1.1 ppm of lead ion. Thetrace amount of lead ion was added to determine preferential binding ofthe silver metal ion over soluble lead ion.

[0065] To 500 ml of the solution containing the above silver metalimpurity and lead ion was added one gram of a divinylbenzenecross-linked polystyrene containing thiouronium functional groups having50% moisture associated with the macroporosity of the additive. Thesolution was stirred for 24 hours at ambient temperature and filtered toremove the macroporous additive. An analysis of the filtrate metalconcentration showed an 86-wt% metal uptake of silver by the additivewith zero uptake of the soluble lead ion. The data shows theirreversible binding of silver to the additive at high hydrogen ion acidconcentration with no detrimental binding of the soluble lead ion resentin the sulfuric acid electrolyte.

[0066] While this invention has been described with respect to variousspecific examples and embodiments, it is to be understood that theinvention is not limited thereto and that it can be variously practicedwithin the scope of the following claims.

What is claimed is:
 1. A battery element useful as a plate in a leadacid battery comprising a separator, active material, sulfuric acidelectrolyte and an acid resistant metal impurity inhibiting amount ofmacroporous organic polymer particles having functional groups on theinternal surfaces of the porous particles which have a preferentialaffinity over lead ion for at least one electrolyte soluble metalimpurity ion more nobler than lead at the discharge chargeelectrochemical and sulfuric acid molarity conditions of the batteryprovided that the metal impurity ion is not substantially detrimentallydesorbed or released from the functional groups under said conditions,soluble lead ion has a substantially reduced affinity for bonding withthe functional groups and said organic macroporous polymer is associatedwith said active material and in contact with the metal impurity ioncontaining electrolyte to allow said ion to substantially permeate theinternal surface of the macroporous polymer.
 2. The element of claim 1wherein the organic polymer has acid functionality.
 3. The element ofclaim 2 wherein the acid functionality is metal impurity complexing. 4.The element of claim 1 wherein the organic polymer has thiouroniumfunctionality.
 5. The element of claim 3 wherein the organic polymer isa cross-linked polystyrene and the cross-linking is by divinylbenzene.6. The element of claim 4 wherein the organic polymer is a cross-linkedpolystyrene and the cross-linking is by divinylbenzene.
 7. The elementof claim 3 wherein the metal impurity is selected from the groupconsisting of antimony and iron.
 8. The element of claim 4 wherein themetal impurity is silver.
 9. A battery element useful as a negativeplate in a recombinant lead acid battery comprising a fiber matseparator, positive and negative active material, sulfuric acidelectrolyte and an acid resistant metal impurity inhibiting amount ofmacroporous organic polymer particles having functional groups on theinternal surfaces of the porous particles which have a preferentialaffinity over lead ion for at least one electrolyte soluble metalimpurity ion more nobler than lead at the discharge chargeelectrochemical and sulfuric acid molarity conditions of the batteryprovided that the metal impurity ion is not substantially detrimentallydesorbed or released from the functional groups under said conditions,soluble lead ion has a substantially reduced affinity for bonding withthe functional groups and said organic macroporous polymer is associatedwith said negative active material and in contact with the metalimpurity ion containing electrolyte to allow said ion to substantiallypermeate the internal surface of the macroporous polymer.
 10. Theelement of claim 9 wherein the fiber in the fiber mat is selected fromthe group consisting of glass, organic polymer and mixtures thereof. 11.The element of claim 10 wherein the fibers are predominantlymicrofibers.
 12. The element of claim 9 wherein the organic polymer hasacid functionality.
 13. The element of claim 12 wherein the acidfunctionality is metal impurity complexing.
 14. The element of claim 9wherein the organic polymer has thiouronium functionality.
 15. Theelement of claim 9 wherein the organic polymer is a cross-linkedpolystyrene and the cross-linking is by divinylbenzene.
 16. The elementof claim 13 wherein the organic polymer is a cross-linked polystyreneand the cross-linking is by divinylbenzene.
 17. The element of claim 9wherein the metal impurity is selected from the group consisting ofantimony, silver, nickel, cobalt and iron.
 18. The element of claim 14wherein the metal impurity is silver.
 19. A battery element useful as anegative plate in a lead acid battery comprising a separator havingpositive and negative active material, sulfuric acid electrolyte and anacid resistant metal impurity inhibiting amount of macroporous organicpolymer particles having functional groups on the internal surfaces ofthe porous particles which have a preferential affinity over lead ionfor at least one electrolyte soluble metal impurity ion more nobler thanlead at the discharge charge electrochemical and sulfuric acid molarityconditions of the battery provided that the metal impurity ion is notsubstantially detrimentally desorbed or released from the functionalgroups under said conditions, soluble lead ion has a substantiallyreduced affinity for bonding with the functional groups and said organicmacroporous polymer is associated with said negative active material andin contact with the metal impurity ion containing electrolyte to allowsaid ion to substantially permeate the internal surface of themacroporous polymer.
 20. The element of claim 19 wherein the organicpolymer has acid functionality.
 21. The element of claim 20 wherein theacid functionality is metal impurity completing.
 22. The element ofclaim 19 wherein the organic polymer has thiouronium functionality. 23.The element of claim 20 wherein the organic polymer is a cross-linkedpolystyrene and the cross-linking is by divinylbenzene.
 24. The elementof claim 22 wherein the organic polymer is a cross-linked polystyreneand the cross-linking is by divinylbenzene.
 25. The element of claim 21wherein the metal impurity is selected from the group consisting ofantimony and iron.
 26. The element of claim 22 wherein the metalimpurity is silver.